Factor in payment (13)
I believe the answer is:
consideration
This clue is a double definition.
'factor' is the first definition.
(thesaurus)
'payment' is the second definition.
(thesaurus)
'in' acts as a link.
(Other definitions for consideration that I've seen before include "Thoughtfulness - relevant factor" , "examination" , "A motive" , "factor to be borne in mind" , "Study" .)